The Prototype

Introduction

In this project, a hybrid solar vehicle prototype including a thermal engine, an electrical motor/generator, a battery pack and photovoltaic panels will be developed and tested. Design, assemblage and testing processes will be presented on this web site, with particular care of didactic sides. Design progresses may be followed through the roadmap and photo gallery. Within project deadline, the prototype will be tested and presented to the media and information agencies.

The Choice

In the first stage of the project, different options have been investigated to build the hybrid solar vehicle prototype. First of all, it has been considered either to build a new vehicle all over again or to develop the project starting from an existing car. Although the first solution appeared to be interesting, it was not feasible and consistent with time and budget limits. Moreover, the second option offered a better chance to apply previous know how and theoretic analyses. At that point, a vehicle typology had to be selected: a kart or a car, with thermal or electrical engine. Finally, an existing electric vehicle was chosen as basic structure for prototype development.

The Structure

A “Series Hybrid Vehicle” configuration seems to be the most suitable solution to match the framework chosen. In this case, traction power is supplied only by the electrical motor (EM/EG), which may operate also as generator during braking mode (regenerative braking), adopting one of the electric vehicle energy recovery strategies. Photovoltaic panels (PV) and the motor/generator system (ICE/EG) either supply power to the electrical motor or charge the battery pack (Battery), accordingly to control system strategies (Vehicle Management Unit, VMU). Further details are available in On-line simulator section.

Series Solar Hybrid Vehicle Typology

The Electric Vehicle

A “Porter Glass Van” by Microvett has been selected to develop the prototype. It is a light duty vehicle suited for urban and protected areas, due to the lack of gas emissions and noise. A “Porter Glass Van” has been provided to the research group by Automobile Club Salerno (ACS), one of the project sponsors.

Porter Glass Van donation to research group by ACS

A significant surface for photovoltaic panels housing is available on the vehicle roof, while motor/generator and control systems may be placed in the large trunk. The powertrain includes an electric motor fed by batteries placed under the driver and passenger compartment. The electric motor may be reached lifting driver seat.

Electric vehicle technical data

Vehicle technical data such as typical sizes, overall volumes, mass distribution, power provided by batteries and so on are listed in the following tables.

Photovoltaic Panels

Referring to photovoltaic panels, different options have been investigated and proper choices have been made:

• What kind of panels has to be used? In order to work on a feasible solution, standard production silicon polycrystalline panels have been selected, rather than high efficiency gallium arsenide panels, capable to assure high performance but extremely expensive.
• A single panel or many smaller panels? The second option has been followed to optimize single panel control as a function of temperature and incoming solar radiation conditions, that may vary on different panels.
• How may panels be mounted on the vehicle? May they be integrated in the roof or an external support has to be provided? First solution guarantees a better aerodynamics and an enjoyable look. Second option assures higher flexibility during design stage and suggests innovative ideas. For example, when vehicle is parked, panel orientation may change following sun position. Finally, a travelling platform has been chosen, taking into account that aerodynamic losses are negligible due to vehicle low speed. Following the roof profile by means of two articulations, an aluminium platform has been built by Saggese company and donated to the research group.
  

The motor/generator system

Firstly, we have tried to use a motor-generator system offered by Lombardini: a 15 KW two-cylinder gasoline engine water cooled. A solution characterized by a favourable power to weigth ratio, by limited sizing and power level adequate to vehicle demand.

Scheme of the Lombardini motor-generator system	Torque, power and specific consumption of Lombardini group

The technical data are summarized in the following table:

 

Lombardini 500cc LGW523 ENGINE Max power 15 [kW] @ 5000 [rpm] 3 phase induction MACHINE 15 [kW] power rated 0 - 6000 [rpm] speed range 200 - 400 [V] DC voltage range 100 [A] DC max current

Lombardini Motor-Generator - Technical Data

In order to remove the heat generated by the the cooling system, the original radiator used on the vehicle has been recovered and mounted, at CIMEP laboratories. Moreover, intake air inlet and exhaust gas discharge outlet have been realized.

The Lombardini group	The generator is mounted on board	Working at CIMEP Labs

This choice has posed some additional problems:

1. the output voltage was higher than the one needed to charge the batteries;
2. electric generator power was higher and not compatible with the circuits already mounted on board;
3. the electric machine needs a complex control system to work as motor during start-up and to shift to generator mode after thermal engine start.

A second motor-generator group

The solution of these problems did not appear compatible with the time scheduling of the project. Therefore, a second solution has been chosen: a 6 KW YANMAR S6000 single-cylinder Diesel engine, air cooled, with electric starter. This generator, although less powerful respect to Lombardini, allowed to overcome the problems cited in 1,2,3. In particular, the electric output, at 230 V, was directly linkable to the vehicle circuitry. Technical data of YANMAR group are available at this link.

The YANMAR motor-generator system	The YANMAR motor-generator system on the back side of the vehicle

The YANMAR has been soon renamed "o' per e o' muss", thanks to its similarity with the groups used by the street vendors of the famous neapolitan speciality. The group has been mounted on the back trunk, using the mechanical supports and the apparatus already available on board. It has been necessary to disable a security block that was preventing battery recharging when the vehicle was moving. Therefore, the engine start has been automated and suitable potentiometers have been mounted on gas and brake pedals.

Noise

Of course, mounting a motor-generator into the passenger compartment is not precisely the best solution in terms of comfort (and safety). Therefore, an acoustic insulator has been designed and realized, with the support of Saggese. A window, with double glass layer, has been inserted to assure back visibility to the driver. A sandwich of insulating material has been chosen, with lead thin layer and a sponge rubber, to cut low and hgigh frequencies. In this way, a satisfying noise reduction has been obtained.

Acoustic insulator

Work in progress...

We are now working to connect an electro-mechanical actuator to regulate engine load and to mount the equipment for data acquisition and vehicle control.

…to be continued